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Insulation using popcorn? + New holographic camera sees unseen with high precision - C C - Nov 17, 2021

(design) Insulation using popcorn?
https://www.uni-goettingen.de/en/3240.html

RELEASE: Building insulation has become an increasingly important topic in recent years. Good exterior insulation reduces heating costs, which means lower CO2 emissions. Nowadays, sustainable natural insulation materials are already available for the interiors of buildings.

But what does sustainability really mean? It means the material should be environmentally friendly and made from renewable raw materials, it must have good thermal insulation and fire protection, and it must be easy to recycle at the end of its useful life.

A research group at the University of Göttingen has long been researching manufacturing processes for products made of popcorn that are sustainable and efficient. The University has now agreed a licence agreement with the Bachl Group for the commercial use of the process and the products for building insulation.

The market is dominated by conventional insulation materials made of plastics or mineral fibre with about 90% of the market share. In fact, plastics derived from petroleum are used for exterior insulation. Could plastic exterior insulation also be replaced by sustainable materials?

A research group at the Faculty of Forest Sciences and Forest Ecology – Chemie und Verfahrenstechnik von Verbundwerkstoffen (chemistry and process engineering of composite materials) – at the University of Göttingen has now succeeded in developing a novel process. Based on its many years of experience in the field of renewable raw materials, the group has managed to develop a process by which insulation boards made of “granulated” popcorn can be produced that have excellent thermal insulation properties and good protection against fire.

The great advantage of this granular material is that it is a plant-based, environmentally friendly and a sustainable alternative to the products derived from petroleum currently used in the industry.

"This new process, based on that of the plastics industry, enables the cost-effective production of insulation boards at an industrial scale," explains the head of the research group, Professor Alireza Kharazipour. "Especially in the field of insulation in construction, this ensures that natural insulation materials are no longer just niche products." In addition, the new popcorn products have water-repellent properties, which opens up even more opportunities for practical applications and extends their useful life.

Michael Küblbeck, group Managing Director of the exclusive divisional licensing partner Bachl, adds: "We are delighted to be launching such an innovative insulation product using popcorn onto the market together with the University of Göttingen. For us, this is another important milestone in our strategic development towards becoming an integrated, multi-material insulation supplier. Popcorn insulation complements our quality range perfectly and means we can respond even more precisely to the different requirements of the market and our customers."


(engineering) New holographic camera sees the unseen with high precision
https://news.northwestern.edu/stories/2021/11/new-holographic-camera-sees-the-unseen-with-high-precision/

RELEASE: Northwestern University researchers have invented a new high-resolution camera that can see the unseen -- including around corners and through scattering media, such as skin, fog or potentially even the human skull.

Called synthetic wavelength holography, the new method works by indirectly scattering coherent light onto hidden objects, which then scatters again and travels back to a camera. From there, an algorithm reconstructs the scattered light signal to reveal the hidden objects. Due to its high temporal resolution, the method also has potential to image fast-moving objects, such as the beating heart through the chest or speeding cars around a street corner.

The study was published on Nov. 17 in the journal Nature Communications.

The relatively new research field of imaging objects behind occlusions or scattering media is called non-line-of-sight (NLoS) imaging. Compared to related NLoS imaging technologies, the Northwestern method can rapidly capture full-field images of large areas with submillimeter precision. With this level of resolution, the computational camera could potentially image through the skin to see even the tiniest capillaries at work.

While the method has obvious potential for noninvasive medical imaging, early-warning navigation systems for automobiles and industrial inspection in tightly confined spaces, the researchers believe potential applications are endless.

"Our technology will usher in a new wave of imaging capabilities," said Northwestern's Florian Willomitzer, first author of the study. "Our current sensor prototypes use visible or infrared light, but the principle is universal and could be extended to other wavelengths. For example, the same method could be applied to radio waves for space exploration or underwater acoustic imaging. It can be applied to many areas, and we have only scratched the surface."

Willomitzer is a research assistant professor of electrical and computer engineering at Northwestern's McCormick School of Engineering. Northwestern co-authors include Oliver Cossairt, associate professor of computer science and electrical and computer engineering, and former Ph.D. student Fengqiang Li. The Northwestern researchers collaborated closely with Prasanna Rangarajan, Muralidhar Balaji and Marc Christensen, all researchers at Southern Methodist University.

Intercepting scattered light. Seeing around a corner versus imaging an organ inside the human body might seem like very different challenges, but Willomitzer said they are actually closely related. Both deal with scattering media, in which light hits an object and scatters in a manner that a direct image of the object can no longer be seen.

"If you have ever tried to shine a flashlight through your hand, then you have experienced this phenomenon," Willomitzer said. "You see a bright spot on the other side of your hand, but, theoretically, there should be a shadow cast by your bones, revealing the bones' structure. Instead, the light that passes the bones gets scattered within the tissue in all directions, completely blurring out the shadow image."

The goal, then, is to intercept the scattered light in order to reconstruct the inherent information about its time of travel to reveal the hidden object. But that presents its own challenge.

"Nothing is faster than the speed of light, so if you want to measure light's time of travel with high precision, then you need extremely fast detectors," Willomitzer said. "Such detectors can be terribly expensive."

Tailored waves. To eliminate the need for fast detectors, Willomitzer and his colleagues merged light waves from two lasers in order to generate a synthetic light wave that can be specifically tailored to holographic imaging in different scattering scenarios.

"If you can capture the entire light field of an object in a hologram, then you can reconstruct the object's three-dimensional shape in its entirety," Willomitzer explained. "We do this holographic imaging around a corner or through scatterers -- with synthetic waves instead of normal light waves."

Over the years, there have been many NLoS imaging attempts to recover images of hidden objects. But these methods typically have one or more problems. They either have low resolution, an extremely small angular field of regard, require a time-consuming raster scan or need large probing areas to measure the scattered light signal.

The new technology, however, overcomes these issues and is the first method for imaging around corners and through scattering media that combines high spatial resolution, high temporal resolution, a small probing area and a large angular field of view. This means that the camera can image tiny features in tightly confined spaces as well as hidden objects in large areas with high resolution -- even when the objects are moving.

Turning 'walls into mirrors'. Because light only travels on straight paths, an opaque barrier (such as a wall, shrub or automobile) must be present in order for the new device to see around corners. The light is emitted from the sensor unit (which could be mounted on top of a car), bounces off the barrier, then hits the object around the corner. The light then bounces back to the barrier and ultimately back into the detector of the sensor unit.

"It's like we can plant a virtual computational camera on every remote surface to see the world from the surface's perspective," Willomitzer said.

For people driving roads curving through a mountain pass or snaking through a rural forest, this method could prevent accidents by revealing other cars or deer just out of sight around the bend. "This technique turns walls into mirrors," Willomitzer said. "It gets better as the technique also can work at night and in foggy weather conditions."

In this manner, the high-resolution technology also could replace (or supplement) endoscopes for medical and industrial imaging. Instead of needing a flexible camera, capable of turning corners and twisting through tight spaces -- for a colonoscopy, for example -- synthetic wavelength holography could use light to see around the many folds inside the intestines.

Similarly, synthetic wavelength holography could image inside industrial equipment while it is still running -- a feat that is impossible for current endoscopes.

"If you have a running turbine and want to inspect defects inside, you would typically use an endoscope," Willomitzer said. "But some defects only show up when the device is in motion. You cannot use an endoscope and look inside the turbine from the front while it is running. Our sensor can look inside a running turbine to detect structures that are smaller than one millimeter."

Although the technology is currently a prototype, Willomitzer believes it will eventually be used to help drivers avoid accidents. "It's still a long way to go before we see these kinds of imagers built in cars or approved for medical applications," he said. "Maybe 10 years or even more, but it will come."